1. Field of Invention
The present disclosure of invention relates to liquid crystal displays (LCD's) and more particularly to LCD's which are subject to manufacturing defects that can result in creation of always-on or always-white pixel areas.
2. Description of the Related Art
A typical liquid crystal display (LCD) has a sandwich like structure that includes a transistor-array substrate, a color-filter substrate, and a liquid crystal layer interposed between the transistor-array substrate and the color-filter substrate.
The transistor-array substrate typically includes a plurality of gate lines, a plurality of data lines and a plurality of pixel areas that are defined by intersections the gate lines and the data lines. A plurality of pixel cell units are provided with each pixel unit being disposed in a corresponding pixel area. Each pixel includes a thin film transistor (TFT) and a pixel electrode whose voltage is to be controlled by the TFT connected thereto, assuming the TFT is operational and/or the drive circuitry connected to the TFT is operational.
The color-filter substrate typically includes a color filters layer, such as one having red, green, and blue light emitting filters or filters of other predetermined colors for use with a back-projected source of white light. A common electrode faces the pixel electrodes. The common electrode is formed on the color filters layer.
During manufacturing of the LCD, a defect of the thin film transistor or a defect of interconnect lines to the TFT may occur so as to render the TFT inoperative. Especially, in an LCD of the type where a turned off TFT corresponds with switching its pixel area into a light transmitting or bright white mode, when a defect that renders the thin film transistor inoperative occurs in one pixel unit, the one pixel operates as a unit having its TFT always turned off during displaying an image. As a result, the one pixel is often more whitely displayed than neighboring pixels during displaying of an average image. Such a pixel defect is sometimes called a “high pixel defect”. When an LCD has one or more such high pixel defects, the image displaying quality of the liquid crystal display is considered degraded.